The present invention relates to a centralized network management and control in a dedicated communications system, and more particularly to the generation of a routing matrix for a centralized network controller.
In a communications network, two routing algorithms are available for determining a route between source and destination. The first is a centralized routing algorithm in which the routing functions of the whole network are concentrated in a single point and the second is one in which routing functions are distributed throughout the network nodes. Each of the routing algorithms is divided into dynamic routing in which the algorithm has a time-dependent variable nature and fixed routing in which the alogrithm is time-independent.
The present invention relates to the centralized, fixed routing alogrithm. As described in Data and Computer Communications, Macmillan Publishing Company, New York and Collier Macmillan Publishers, London by William Stallings, pages 258 to 259, fixed routing is one of the simplest routing strategies in which a route is selected for each source-destination pair of nodes in the network. The routes are fixed, or at least only change when there is a change in the topology of the network. A central routing directory is created to be stored at a network control center.
To achieve efficient utilization of network resources, it is important that any destination be reached from any source by a mininum number of links, or "hops", and a method of doing this is described in Computer Networks, Prentice-Hall, Inc., by Andrew S. Tanenbaum, pages 38 to 40. According to this method, a route is determined on a link-by-link basis. One disadvantage of this method is that if the number of nodes increases, the process steps involved increase in a geometrical progression. In addition, if alternative routes are available for a given pair of nodes, there is no appropriate yardstick available to evaluate the alternatives to determine the optimum route. In such instances, the usual practice is to employ a method by which the route of first encounter is selected or a method by which one of the alternative routes is randomly selected. If this prior art routing is applied to a network of FIG. 6a, a routing directory of FIG. 6b will be derived and link usages will be unevenly distributed as shown in FIG. 6c, resulting in inefficient utilization of network resources and increased lost calls.